PROJECT SUMMARY This RM1 proposal focuses on defining and characterizing the integrated systems that support intracellular organelle transport and placement. Rather than just characterizing ?molecules? as biophysicists or ?organelle dynamics? as cell biologists, our goal is to achieve an atomic-to- cellular-to-in vivo level understanding of the mechanisms of organelle transport. Our collaborative and multi-disciplinary research team will discover and study the native microenvironments in cells and in vitro, by considering physiologically-relevant combinations of molecular motors, filaments, adaptors, membranes and other cofactors that control organelle movement and polarization. We will use mitochondria as our initial model system, as many key molecules and signaling pathways that are essential for the dynamics of this organelle have already been described. We will uncover the roles of spatial organization and dynamic assembly of filaments, mechanical forces, motor activity, and other regulatory elements will be investigated. We will reconstitute complex microenvironments in vitro to determine motile and anchoring mechanisms. We will computationally model these systems and experimentally test models directly in cells and in vivo. Our research team will be energized and expanded by implementing an Exploratory Pilot Studies Program to incorporate promising early-stage- investigators into our collaborative team.